degenerative arthritis 退化性關節炎

One and a half month ago, I started to have pain when moving my left shoulder in some directions. I consulted a general practitioner who referred me to have an x-ray check. The report mentioned that I've got degenerative arthritis (退化性關節炎) on my left shoulder. I told the GP that I hurt my left shoulder when I was a teenage, and the GP said this was the cause of the problem. The GP has given me Voltaran tablets (prescriptive medicine). I have eaten for ten days but the effect was very small. I consulted the GP again, who just gave me more Voltaran. But, the GP also advised me to try Glucosamine and Chondroitin tablets, which can be brought from the street and needs 2-4 weeks for expected results. I have eaten the G and C tablets for one week (stop using Voltaran), but my shoulder has had little improvement. I can move my left shoulder forward and backward, so it does not affect my running training. However, I cannot turn my left arm to my back and cannot swing it to the left and right. I cannot put up my left arm straight. Since Monday, I started to have pain in doing pushup, and I stopped to do it now. I am now writing to see if anyone has a similar experience or if anyone knows how to improve my situation. I am 43 years old and I would like to know if my problem can be solved.